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STI Engineering

Steam Injection

                                                       Enhanced Landfill Gas Production
                                                             With Steam
                                                               (continued)

SITE CHARACTERIZATION

The study area was in a 12-acre portion of the landfill that had not been disturbed by LFG collection. The
waste was approximately 150 feet thick in a lined portion of the landfill. About 8 feet of cover soil/stockpile
was placed over the whole area. This landfill receives only 4-8 inches of rain per year. A dense layer was
indicated by the PPT at 52 feet below ground surface, which acted as a false bottom so only the top 50 feet of
the landfill was treated with steam.

The PPT locations were designated as EW (extraction well) if a collector was installed following the PPT
sounding. The PPT locations were designated as SI (steam injector) if a steam injector was installed at that
location. Also the PPT locations were designated as Piezo if a static Piezometer was installed at that
location. (see Site Layout, Figure 12)

Seven large diameter gas collectors were already installed at the northern end of the test area. To determine
their range of vacuum influence PPT soundings were performed at 50’, 40’ and 25’ from the existing
collectors adjacent to the test area. Significant vacuum was only indicated in the sounding that was only 25
feet from the collector. Based on this data the test area was placed at least 100 feet away from the line of
existing collectors to minimize their influence on the test area.

PROGRESS OF OBJECTIVES AND GOALS

The following bullet items are the initial objectives for this Pilot Study and the current performance results for
each objective, based on the progress achieved:

1. Increase the moisture content of the refuse

Based on temperature increases noted from thermocouple points (see Table, Figure 8), the moisture
content of the refuse appears to be increasing within a 75-foot radius around each injector. The moisture
increase comes from steam moisture and bio-degradation of refuse, both related to the increase in refuse
temperature.

2. Increase the temperature of the refuse

The temperature data also indicates that there are areas within the test site that have increased in
temperature by as much as 69o F. Additional information regarding temperature increases in specific areas
will be analyzed during the upcoming PPT investigation performed near the completion of the Study.

3. Monitor the migration of the steam through the refuse horizontally and vertically

The steam migration through the refuse, both horizontally and vertically, has been continually monitored
during the Study period. Temperature increases have been detected at 15 and 35 feet below ground surface.

4. Control the steam migration by using LFG collectors

It has been demonstrated that increasing or decreasing vacuum flow at the LFG collectors can control steam
migration through the refuse.

5. Monitor any excess liquid at bottom of test site

Piezometer readings do not indicate the presence of any liquid collecting beneath the refuse layer and
comes in contact with the impervious fill cap soils, which is 50ft below ground surface.

6. Evaluate whether or not landfill leachate and condensate can be used in this process

This has been the greatest challenge and appears to have been resolved. At this point, the leachate and
condensate from the landfill can be used in this process assuming the landfill can provide a sufficient
amount of leachate and the filtration operation can maintain production. Since the leachate is no longer
being re-circulated the daily output of leachate has diminished rapidly.

7. Increase the LFG quality and quantity output within the test site

The primary goal of this Pilot Study is to control the flow of the collectors to manage steam migration,and is
not intended to obtain the highest flow rate of LFG.   However, as a positive addition, some of the LFG
collectors have indicated a 10% increase in methane concentrations. This appears promising, although
each time the collector valves are closed to retain the heat generated because water inflow has ceased,
either due to insufficient water provided or system down time for repairs/maintenance, flow rates become
difficult to accurately calculate. As production times become stable and longer, more consistent
measurements can be made. More definitive information will be available at the time of the Final Report.

8. Increase the settlement of the refuse

There is visible evidence along the line of steam injectors of about 18” to 24” of settlement. Soil settlement
has not yet been detected at the settlement monuments; however, the Study was focused on the viability of
the process and the potential environmental impact of moisture added to the refuse. The reduced volume of
leachate water available for the Study prevented settlement from spreading out far from the injection wells at
this time. Additionally, the existing surface soil cap is likely bridging over the refuse. Significant settlement is
anticipated when surface compaction efforts collapse the soils.

9. Obtain material quantities and costs per acre for treatment

A cost analysis will be presented after the study is concluded. Initially, the additional costs for larger boilers
and filtration systems to overcome the high solids content of the leachate water, and, the recent substantial
increase in fuel costs have had an impact on the initial cost estimates for the Study.

10. Obtain landfill surface settlement values during a 3 to 6 month period.

Due to filtering of the leachate water, the Study is about two months behind schedule. As long as there is
insufficient water to convert to steam, the Study will not achieve its desired potential. Surface settlement
values will not be accurate or significant if the Study cannot continue as planned with appropriate supply of
water. Monitoring will continue and be reported at the completion of the Study.

1ST PROGRESS REPORT CONCLUSIONS

As stated above, despite production issues and delays, most of the Study’s objectives have been achieved.
With the modest amount of water injected and settlement achieved, the initial results are still encouraging.
Once there is enough water to operate 24-hours a day for several of weeks, another PPT Profile will be
performed to evaluate actual subsurface conditions relative to the anticipated results.

It is becoming apparent that the soil layers used to cap the landfill at various times, are bridging over the
underlying refuse layers and inhibiting settlement despite the increase in void space within the refuse
zones. Therefore, in order to fully realize the actual volume reduction potential, some form of mechanical
compaction may be necessary to break through the soil layer and allow total settlement to occur. Evaluation
of the impact of this condition will be conducted as production is increased and the system is operating at full
capacity.

CONTINUING OPERATIONS

In order to optimize conditions for landfill volume reduction by bio-degradation, it is imperative to provide
sufficient steam to the test prism such that virtually all voids can be filled with moisture. The steam injection
operations began at the site using a 360,000 Btu boiler capable of delivering over 4,000 gallons of steam per
24-hour period. The boiler performance was considered optimal based on calculations regarding the
amount of void space estimates within the total waste volume, approximately 20%.

The water supplied for the steam injection comes from the landfill leachate collection system and, as a
result, has a very high amount of both particulate and dissolved solid matter suspended within. This water
introduced solids into the boiler and injection system causing significant mechanical problems, machinery
clogs, and resulting down time needed to clean and repair the equipment. The degree of filtration was not
apparent or planned for in the initial design of the system.

Filtering the water is the only viable solution, but has been hampered by extremely high, suspended solids
over-loading all devised filtration systems. The system could not operate for the planned extended periods
due to the maintenance of filtration and injection equipment. However, the majority of filtration problems have
been overcome and the system is functioning more reliably.

Only about 350,000 gallons of water was injected as steam, which is well below the 800,000 gallons initially
planned. At the start of the study the landfill leachate collection system was recovering about 13,000 gallons
per day, which the landfill operators were re-circulating at the active face. Once the leachate was being
delivered to the study site and converted to steam, the daily leachate rate went down to approximately 500
gallons per day. Condensate from landfill gas was used to supplement water needs. The condensate
actually became more of an asset than just being additional water, as its lower pH cleaned the boiler coils
and steam pipeline.

With this addition the landfill was only producing an average of about 1,500 gallons of leachate and
condensate per day, insufficient to achieve the planned objectives, whereas, the planned steam injection
process was permitted for 3,400 gallons per day minimum, yielding a water shortage of 1,900 gallons per
day. A request was submitted to the City to use locally available recycled water as a supplement to the
leachate and condensate water. This would allow for production goals to be achieved. This request was
rejected by the Regional Water Quality Control Board, due to the short term of the pilot study. The Board
stated that the application would be considered if or when the project went to full scale.

Our experience with the smaller boiler indicated increasing the temperature (375oF) in order to expand the
steam influence in the waste prism was not the way to increase coverage. By increasing the temperature we
were creating particular matter and carbonate deposits inside the boiler. By lowering the temperature to
250oF the boiler stopped fouling.

When the temperature was lowered, which consequently reduced steam pressure in the small boiler it was
necessary to increase the size of the boiler and water flow, as to increase the steam influence in the test
site. A 660,000 BTU unit was ordered but had a 1 month lead time, so a used 440,000 BTU unit was used
until the larger unit arrived. The larger unit did increase the steam influence.

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